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Based on an integrative taxonomic approach, we examine the differentiation of Southeast Asian snail-eating turtles using information from 1863 bp of mitochondrial DNA, 12 microsatellite loci, morphology and a correlative species distribution model. Our analyses reveal three genetically distinct groups with limited mitochondrial introgression in one group. All three groups exhibit distinct nuclear gene pools and distinct morphology. Two of these groups correspond to the previously recognized species Malayemys macrocephala (Chao Phraya Basin) and M. subtrijuga (Lower Mekong Basin). The third and genetically most divergent group from the Khorat Basin represents a previously unrecognized species, which is described herein. Although Malayemys are extensively traded and used for religious release, only few studied turtles appear to be translocated by humans. Historic fluctuations in potential distributions were assessed using species distribution models (SDMs). The Last Glacial Maximum (LGM) projection of the predictive SDMs suggests two distinct glacial distribution ranges, implying that the divergence of M. macrocephala and M. subtrijuga occurred in allopatry and was triggered by Pleistocene climate fluctuations. Only the projection derived from the global circulation model MIROC reveals a distinct third glacial distribution range for the newly discovered Malayemys species.
Movement patterns, home range sizes and habitat use of the Elongated Tortoise, Indotestudo elongata, (Blyth, 1854) was studied in northern Cambodia. Therefore, ten adult tortoises, which had been confiscated from the local illegal trade and kept at a wildlife rescue centre for several years, were fitted with VHF radio tracking transmitters, and released to the Kulen Promtep Wildlife Sanctuary at the onset of the rainy season. Between August and December 2009 the tortoises were subsequently located between 41 and 54 times each. An incremental area analysis with a randomized resampling approach with 100 iterations was performed to assess whether home range size estimates reached asymptotes. Computer-simulated random walk models were performed with 'distances of successive locations' and 'turning angles' calculated from obtained radio tracking data to determine whether the studied tortoises performed nomadic movements or exhibited home ranges. Subsequently, seasonal as well as total home range sizes were determined using minimum convex polygon estimators and fixed kernel density estimators.
The feeding ecology of Indotestudo elongata was assessed through direct observations and faecal sample analyses at the Kulen Promtep Wildlife Sanctuary, northern Cambodia and the Cat Tien National Park in southern Vietnam. The species was confirmed to maintain an omnivorous diet comprising terrestrial thin shelled snails, common earthworms, carrion, mushrooms, rice field crabs, and foliage of different plant species. Observations suggest that food items consumed by I. elongata vary according to their seasonal availability.
The Euphrates Soft-shelled Turtle, Rafetus euphraticus, is an endangered tryonchid turtle endemic to the Mesopotamian River Basin in the Middle East. Within recent decades, populations of this aquatic species have been heavily depleted and severely fragmented due to habitat alteration and destruction by drainage and hydroelectricity dam constructions. Presently, ongoing habitat loss and fragmentation are considered the main drivers for the species' population decline. In order to assess whether evolutionary significant units exists, intraspecific genetic variability was evaluated using two mitochondrial gene fragments for 31 specimens covering most of the species' distributional range. In addition, habitat suitability models were computed using a combination of bioclimatic and remote sensing variables as environmental predictors to determine habitat suitability, fragmentation and coverage by designated protected areas across the species' range to ease future conservation measures.
Movement and habitat selection of the endangered Euphrates Softshell Turtle Rafetus euphraticus (Daudin, 1802) was studied at the Karkheh Regulating Dam Lake in southwestern Iran. Twelve adult turtles were trapped, fitted with VHF radio tracking transmitters, and relocated between 21 and 51 times between May 2011 and July 2012. An incremental area analysis with a randomized resampling approach with ten iterations was performed to determine whether home range size estimates reached asymptotes. Computer-simulated distribution models were applied to assess whether turtles performed nomadic movements or exhibited home ranges. We determined the turtles' linear range sizes, river channel areas, minimum convex polygon home range sizes and kernel density estimator home range sizes. Habitat selection was assessed using a Chi-square goodness-of-fit test with confidence intervals determined using a Bonferroni z-test.
Anthropogenic climate change has already led to alterations in biodiversity patterns by directly and indirectly affecting species distributions. Poikilothermic animals, such as reptiles, have been suggested to be particularly vulnerable and large-scale reptile declines have already been observed. Currently, half of the world's freshwater turtles and tortoises are considered threatened with extinction, and climate change may exacerbate these declines. To assess how global chelonian species richness will change in the near future, species distribution models were developed under current climate conditions for 78% of all extant species and subsequently projected onto different Intergovernmental Panel on Climate Change (IPCC) scenarios for 2080. A strong dependence of temperature shaping most species ranges was detected, which coincides with their general temperature-related physiological traits (i.e., temperature-dependent sex determination). The extent and distribution of the current bioclimatic niches of most chelonians may change remarkably in the near future, likely leading to a substantial decrease of local species abundance and ultimately a reduction in species richness. Future climatic changes may cause the ranges of 86% of the species to contract, and of these ranges, nearly 12% are predicted to be situated completely outside their currently realized niches. Hence, the interplay of increasing habitat fragmentation and loss due to climatic stress may result in a serious threat for several chelonian species.
The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5-10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic bottlenecks; and (iii) predict threats due to anthropogenic climate change in the future.
More about paleophylogeographic modeling and animated models for all Nearctic turtle species can be found here.
With estimates of fewer than 1000 mature individuals, the critically endangered Siamese Crocodile, Crocodylus siamensis Schneider, 1801 is one of the least known and at the same time most threatened crocodilian species in the world. Populations have already been depleted to approximately 20% of their former size with habitat destruction, alterations, and loss being the main drivers of population declines. To evaluate habitat suitability and coverage by designated protected areas across the species' distributional range habitat suitability models were computed using a combination of bioclimatic and remote sensing variables as environmental predictors. Additionally, population connectivity as well as current and future habitat fragmentation through dam construction was assessed by performing population connectivity models to facilitate future conservation management strategies and prioritization.
Intensive herpetological field research was conducted at the Kulen Promtep Wildlife Sanctuary in northern Cambodia between 2009 and 2011. As a result, a checklist comprising 22 species of amphibians and 33 species of reptiles belonging to 44 genera in 22 families was compiled. The checklist includes three species (Ingerophrynus macrotis, Micryletta inornata, Scincella melanosticta) which in Cambodia were formerly known exclusively from the Cardamom Mountains.
© 2014-2016 Flora Ihlow
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